Earliest known fossil trackways discovered in China

Chinese researchers have discovered the world's earliest fossilized animal trackways dating back as far as 551 million years in the area of Three Gorges of Yangtze River in central Hubei Province.

The trackways, characterized by two parallel rows of imprints, were found on a dozen fossils, said Chen Zhe, leader of the research program and a member with the Nanjing Institute of Geology and Palaeontology under the Chinese Academy of Sciences.

Chen Zhe, a researcher with the Nanjing Institute of Geology and Paleontology at the Chinese Academy of Sciences, shows the earliest known footprints left by an animal on earth, which date back at least 541 million years, in Nanjing, Jiangsu Province, June 7, 2018. Researchers from the institute and Virginia Tech University in the United States found the tracks in the Three Gorges area and published their report in the US journal Science Advances. [Photo: Chinanews.com/Yang Bo]

Chen said the team made an animation to simulate the creature's movement based on the two lines of dots. The animal was two centimeters long and one centimeter wide.

"We suspect that the animal may have burrowed under marine algae to find oxygen and food," he said.

Since there has been no fossil record of such animals, the scientists do not know exactly what left the traces, but they know the trackways were left by paired appendages.

"Appendages are important for paleontological study, as they could have significant impact on geochemical cycles and ultimately the global environment," Chen said, citing the example of termite mounds, which can move and shape sediment.

Chen Zhe, a researcher with the Nanjing Institute of Geology and Paleontology at the Chinese Academy of Sciences, shows the earliest known footprints left by an animal on earth, which date back at least 541 million years, in Nanjing, Jiangsu Province, June 7, 2018. Researchers from the institute and Virginia Tech University in the United States found the tracks in the Three Gorges area and published their report in the US journal Science Advances. [Photo: Chinanews.com/Yang Bo]

He explained that the animal could walk and burrow. When it burrowed, it targeted microbial mats where microorganisms made organic carbon and molecular oxygen. Molecular oxygen was scarce back then.

The research was jointly carried out by the institute and Virginia Tech, and a research paper was published on the international science journal Science Advances on Wednesday.

Chen said most life forms on Earth can trace their ancestors back 540 million years ago to a period known as the Cambrian explosion, when many new and diverse types of animals appeared for the first time.

Chen said based on the study of geological layers and dating of the fossil-bearing rock, the team estimated the fossils date back 541-551 million years ago, making them 10 million years older than previously known trackways.

Chen Zhe, a researcher with the Nanjing Institute of Geology and Paleontology at the Chinese Academy of Sciences, shows the earliest known footprints left by an animal on earth, which date back at least 541 million years, in Nanjing, Jiangsu Province, June 7, 2018. Researchers from the institute and Virginia Tech University in the United States found the tracks in the Three Gorges area and published their report in the US journal Science Advances. [Photo: Chinanews.com/Yang Bo]